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Antioxidant antidote: staving off effects of sidestream smoke. (Science Selections).

Dietary antioxidants have long been promoted as a defense against many diseases, such as cancer, cardiovascular disease, and diseases of the immune system. A new study provides evidence that in animals, multiple antioxidants can help lessen the harmful effects of secondhand cigarette smoke, and they may lessen the effects of secondhand smoke in humans [EHP 109:1007-1009]. The study, by Jin Zhang and colleagues at the College of Public Health at the University of Arizona Health Science Center, explores for the first time certain cellular responses in aged mice to sidestream cigarette smoke (one component of secondhand smoke), and the effect of antioxidants in reducing these responses.

The researchers found that exposure to moderate levels of sidestream cigarette smoke increased harmful oxidation and also promoted the production of interleukin-6, an inflammatory mediator closely linked to cardiovascular disease. The study showed that multiple antioxidants given as dietary supplements prevented these changes. The 11 antioxidants fed to the mice in the study were beta carotene, bioflavonoids, coenzyme Q10, D-alpha-tocopherol, L-ascorbic acid, L-carnitine, magnesium, N-acetylcysteine, retinol, selenium, and zinc.

Cigarette smoke does much of its damage via free radicals in the form of reactive oxygen species. These highly reactive oxygen molecules are believed to play an important role in the development of a wide range of diseases. Reactive oxygen species can overwhelm the cell's antioxidant defenses. They can also start the cellular chain reaction that leads to inflammation. Not only is tobacco smoke among the greatest external sources of free radicals, it also works internally, causing the body to produce reactive oxygen species that may increase damage inside cells.

From earlier research, the investigators hypothesized that multiple antioxidants, rather than a single one, may be required to prevent the damaging oxidation and proinflammatory response that sidestream smoke causes. To investigate whether moderate intake of sidestream smoke starts a proinflammatory response and promotes oxidative damage, the researchers looked at three cellular defense mechanisms--hepatic lipid peroxide production, vitamin E level, and interleukin-6 production--in both "nonsmoking" and "smoking" mice.

The mice used in the study were healthy and old (13 months of age at the start of the study). They were divided into four groups: nonsmoking mice fed or not fed multiple antioxidants, and smoking mice--exposed to a burning cigarette for 30 minutes a day, 5 days a week, for 4 months--either fed or not fed multiple antioxidants.

The researchers found increased production of interleukin-6 in the spleen and lipid peroxides in the liver in the smoking mice. Lipid peroxides result when a cell's antioxidant defenses are overwhelmed by reactive oxygen species. Interleukin-6 is a proinflammatory cytokine, produced as an immune response to inflammation. The study also found that in smoke-exposed mice, vitamin E, a powerful antioxidant, was depleted. This suggests that the cell antioxidant defense system is affected by sidestream cigarette smoke exposure.

Adding multiple antioxidants to the diet turned these effects around. For both smoking and nonsmoking mice fed antioxidant supplements, lipid peroxide production was significantly lower, while vitamin E levels were significantly higher. In addition, smoke-exposed mice fed antioxidant supplements showed significantly lower production of interleukin-6 compared to smoke-exposed mice on a control diet. The authors suggest that supplementing the diet with multiple antioxidants may reduce the effects of exposure to sidestream cigarette smoke in humans as well.
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Author:Alderson, Laura
Publication:Environmental Health Perspectives
Date:Oct 1, 2001
Words:545
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